Review on 🔹 EHEIM Substrat Pro 2L - High-performance Biological Filter Media (Sintered Pearl-Shaped Glass) by Bogusawa Daczkowska ᠌

I have been using it for over 5 years. I change the filler 1 time in 3-4 years. Since I have 3 baskets with filler in the external filter (1 basket - ceramic rings, 2 and 3 - SubstratPro), I advise you to change first in basket 3 (the last one in terms of water flow) when replacing, and then after about a month change in the remaining one - so you will least damage the nitrogen cycle in the aquarium.